or, is it possible to fence the new ones separate with some wire netting so they can be seen by the old flock? Throw some wheat or whatever you feed close to the wire netting so the chooks have to eat close by each other. You'll see by the behaviour when they have been accepted. Even then, there may be some squabbling when you remove the wire, but not as bad.
In the days when we kept a rooster there was very little trouble introducing new hens. He had his evil way within 5 seconds and if the other hens chased the new one he would sort it out. Normal squabbling is ok to establish who is the second in charge etc.
As a peculiar observation... When a new rooster was introduced because the older one graced out dinner table, the second in charge hen usually lost her status too and could easily end up third or forth in line.
Then there was this little bantam rooster who had the ego of an buffalo.... but that's another story.